Preparation Of High Strength Aluminum Alloy And The Study On Its Performance

In recent years, the global aluminum industry has stepped into a new period of rapid development. Through constant research and development on material of aluminum alloys, it not only improves the performance and the application range of the aluminum, but also expands its usage. It makes great contribution to the development of world economy and the progress of mankind which is considered as the most abounded in development and application potential of the "green material" in the21st century. Al-Zn-Mg-Cu, as a high strength aluminum alloy with small specific gravity, high strength, and good thermal processing performance, is widely applied in aviation fields and civil industry. The pursuit of material strength, toughness, high corrosion resistance and formability has always been the theme of the study. In order to provide basis for the industry application, further study on process control technology of high strength aluminum alloy should be needed. In this paper, the influence of chemical composition, rolling process and heat treatment process on the microstructure, mechanical property, exfoliation corrosion resistance, electric property and room temperature formability were investigated. The main conclusions are as follows:(1) With increasing the total cold processing ratio of finished goods, in the T6peak aging condition, both the tensile strength and elongation of the alloy first increase and then decrease,30%total cold processing ratio of finished goods has a better comprehensive mechanical property, with σb=605.3MPa, σs=509.4MPa, δ=6.3%. Both the conductivity and exfoliation corrosion resistance are superior of10%total cold processing ratio of finished goods, and the formability of alloy is better in condition of solid solution with cup value CCV=50.1, minimum relative bending radius Rmin/t=3.2. When total cold processing ratio of finished goods reaches50%, it may cause precipitation mechanism change, leading to the main strengthening phase cannot nucleate and precipitate effectively.(2) With increasing regression temperature, the regression time for alloy plate to reach peak strength after ending aging is shorter. At180℃,200℃,220℃regression temperature, the proper regression time is15min,7min, lmin, respectively. In15min regression time, the strength and elongation of alloy plate remain at high values after ending aging. When regression time is more than30min, over-regression occurs, and the comprehensive mechanical property of alloy declines distinctly. At220℃×1min regression, the strength of alloy reaches its maximum value after RRA, σb=647.0MPa, σs=602.3MPa. At200℃×7min regression, the alloy has a better comprehensive mechanical property, σb=606.5MPa, σs=585.9MPa,δ=6.9%. With the regression temperature rises, conductivity of alloy plate first increases and then decreases; with the regression time increases, conductivity appears an increasing curve. After RRA heat treatment120℃×24h+200℃×7min+120℃×24h,the conductivity reaches the highest value of42.05%IACS. The exfoliation corrosion resistance of RRA is better than T6.(3) With increasing Cerium content, as-cast grain refinement is obvious, secondary dendritic spacing decreases.The bulky eutectic structure which is meshy continuous distribution along the grain boundary also reduces. After RRA, in the range of0.15%-0.35%Cerium content, the strength increases slightly, while the elongation first decreases, then increases. When Cerium content reaches0.45%, the comprehensive mechanical property of alloy declines distinctly. The addition of rare earth Ce has no beneficial effects to Al-Zn-Mg-Cu alloy plate on electrical properties and exfoliation corrosion resistance, since conductivity reduces slightly and exfoliation corrosion phenomenon occurs more seriously.